The city's Medical Officer of Health has issued a cold weather alert for Hamilton.
This, as windchill values hover in the 'minus 15-20' range.
The alert means community agencies who work with homeless people such as the Salvation Army are implementing their cold weather policies and procedures.
If you see someone in need of shelter, you're asked to call the Salvation Army.
The cold will ease tonight as temperatures rise above zero.
However, the coldest blast of Arctic air yet this season is in store Monday and Tuesday -- with highs not expected to make it past minus 10.